Cathode-ray image converter tube



Oct. 7, 1952 H. BRUlNlNG Erm. 2,613,330

CATHODE-RAY IMGE CONVERTER TUBE Filed mbv; 4, 195o ,JNVENTURS HAJO BRUINING -FLORIS DE BOER PIET. R SCHA EN WWW AGENT Patented Oct. 7, 1952 UNITI-12D {STATES PATENT 'oF'FIcEI l .2,613,330 l CATHODE-RAY IMAGE' TUBE 1 Hajo Bruining, loris de Boeigand Schagen,

. EindhovemNetherlands, assignors .to Hartford National Bank and Trust Company,"=Hartford,

Conn., as trustee ,Application November 4, 195o, serial No. 194,074..

`Intlle Netherlands November 25,11949 j 'solaires'. (Crais-:65)

The present invention relatesjto. cathodaray tubes and more particularly to cathoderayimage converter tubes and to a method for manufacturing the same. f y

Cathode ray image converter tubes serve .as opticall instruments for .converting light images of one Wavelength intolightimagesof another, usually visible, wavelength and `for amplifying images of low brightness. These tubesusually comprise a photo-electrically active layer responsive to the impinging radiation, an electron lens system for focussing the. electrons emittedby the photo-electric layer into an electron image and a iiuorescent projection screen for converting the electron image into an image ofthe desired wavelength, usually visible.` Whensu'ch tubes comprise a cathode sensitive toinfra-red radiation, they may be used for observing objects in the dark or mist.

To indicate the center of the eld of view of the image converterV tube, it has been proposed to provide cross-Wires on the fluorescent screen. Other marks such as graduations or small divisions have been similarly provided. However, this arrangement has not proven satisfactory due to displacement of the electron image relatively to the fixed mark under the. action of. undesired electric or magnetic fields.. v,Such a displacement may, for example, be causedby the terrestrial magnetic eld.

To obviate this disadvantage, it has been proposed to project an image of cross-wires onto the photo-electrically active layer by means of an additional lens in the optical system arranged in front of the tube. Since a displacement of the fluorescent image involves a shift of the image of the cross-wires, the position of the wire cross thus remains unchanged with respect to the field observed. This arrangement has the disadvantage of requiring an additional lens thereby making the optical system more complicated' and costly.

In accordance with the invention, the above disadvantages are obviated by providing at the carrier of the photoelectrically active layer an object which projects itself electronoptically as a mark onto the projection screen.

As a rule the carrier for the photoelectric layer is constituted by the wall of the discharge tube. In this event, a figure projecting itself as a mark may be provided at the exterior of this wall. This is an extremely simple method, but has the disadvantage that the plane of the ligure does not coincide with the place of the photoelectric layer so that a sharply focussed image of the figure is notl formed .on the `fluorescent screen.

Furthermore, thegthickness of the tube wall is usually. `too great'to Yobtain Va .sufhciently sharp shadow 'of ,the figure."

1 Therefore,. in accordance. with fthe preferred embodiment of .the invention, ,the figure `tojbe projected .is ,located underneath the photo-electrically sensitive layer .on the carrier vthereby'in- ,terce'pting the impingi'ng light .'rfays.v The ligure to be projected asfa `mark may alternatively, be I `produced. .in a differeriftlma'nner,y for .example by the local removalof thephoto-ele'ctric material in accordance with the desired pattern or `by ,providing ,a material, `pre-ventingA ,activation of .the

`photo-ele'c`stric ,material at a given areavthereof.v

,2; is internally coated with a thin butopaque aluminum 1ayer`4."' A supply conductor` tiy passed through the wall.. th. tube inV a vacuum-tight mannenlis connectedto this layer. A window 6 has been ,leftF free "atjthe,centreof the opaque layer. A second've'ry thin 4transparent layer extends over the layer 4 and the window 6, this second layer having been produced by precipitating silver or a different suitable metal and sensitised under the action of oxygen and caesiurn vapour in a known manner such as to act as a photo-electric cathode.

The thickness of the layers 4 and 'l is exaggerated in the drawing. The opaque layer actually has, for example, a thickness of 0.1 micron, the layer 'l usually having a thickness only of several atoms.

The bottom part 3 comprises a flat plate 8 carrying the fluorescent screen 9. Furthermore, it carries a metal hood I D constituting the anode or electron focussing member of the tube. The spherical cap Il of the anode and the concave cathode surface jointly constitute an electronoptical system by which the cathode-rays passing through an aperture I2 provided in the anode cap are focussed in such manner as to produce an image of the window 6 on the screen 9. A supply conductor I3 passing through the bottom part 3 in a vacuum-tight manner is secured to the anode.

The window 6 is formed during the application ofthe layer -4 and this is eifected by means of a mask arranged on the inner wall of the spherical part 2, which mask is removed prior to applying the photo-electrically active layer. This mask has an aperture consisting of four slits jointly forming a small cross with the point of intersection in the axis of the tube, thus creating on the wall of the tube a figure I4 corresponding to the aperture of the mask on applying the layer 4. This figure intercepts extraneous light rays and when vprojecting an image onto the sensitive layer 1 by means of a suitable optical system (not shown). The same figure is observed through the transparent plate 8 on the fluorescent screen 9 as a cruciform mark.

The gure I4 and the layer 4 are preferably formed by vacuum vaporization of a suitable metal, for example, by vaporizing aluminum, silver or the like from a suitable chamber electrically heated by a tungsten 'filament'. Subsequently, the mask is removed 'and the bulb is closed by a bottom comprising 'the anode iIl and a fluorescent screen 9. After the tube has again been exhausted, another layer of metal, for example, o-f silver or antimony is precipitated onto the cathode carrier 2, butnow to such a thinness as to be transparent. It is customary to form this deposit by heating a piece of metal arranged in the bulb, for example by means of a high-frequency magnetic ield.V l Y The so deposited Wall-coating is madejphotoelectrically active by introducing oxygen and subsequently caesium vapour into the tube. It now emits electrons when extraneous light 'falls on the cathode, but only where the latter is free fromthe opaque layer, that is the areaof the removed mask, except for the :ligure recessed therein, Where extraneous light rays cannot penetrate to the photo-electrically active layer, `so that the latter is made inactive. v i v u What We claim is: v,

1. A cathode ray image converting device comprising a carrier member, a photoelectric layer mounted on said carrier member and having an active area with a given boundary, said carrier member having within the .boundary of said area a portion defining a non-photoelectrically active figure of given conguration on said photoelec- .4 electron focussing member interposed between said layer and said screen.

2. A cathode ray image converting device comprising a carrier member, a photoelectric layer mounted on one side of said carrier member and having an active area with av given boundary, said carrier member having on the said one side and within said area a portion defining a nonphotoelectrically active iigure of given configuration on said photoelectric layer, an electron-responsive screen, and an electron focussing member interposed between said layer and said screen.

' layer of opaque material o-n said carrier member tric layer, an electron-responsive: screen, and van y and surrounding said active area, said carrier member having on the said one side and within said area a portion of opaque material defining a non-photoelectrically active gure of given coniiguration on said photo-electric layer, an electron-responsive screen, and an electron focussing member interposed between said layer and said screen.

4. A cathode ray image converting device comprising a transparent envelope portion, a photoelectric layer mounted on one side of said envelope portion and having an active area with a given boundary, an opaque layer of aluminum on said envelope portion and surrounding said active area, said envelope portion having on the inside thereof and Within said area an aluminum deposit defining a non-photoelectrically active figure of given configuration on said photo-electric layer, a fluorescent screen, and an electron focussing member interposed between said layer and said screen. i

HAJOv BRUININ G. FLORIS DE BOER. PIETER SCHAGEN.

REFERENCES CITED UNITED STATES PATENTS Name Date Lubszynski Mar. 28, 1939 Number 

